Semiconductor device and a method of manufacturing the same

ABSTRACT

For simplifying the dual-damascene formation steps of a multilevel Cu interconnect, a formation step of an antireflective film below a photoresist film is omitted. Described specifically, an interlayer insulating film is dry etched with a photoresist film formed thereover as a mask, and interconnect trenches are formed by terminating etching at the surface of a stopper film formed in the interlayer insulating film. The stopper film is made of an SiCN film having a low optical reflectance, thereby causing it to serve as an antireflective film when the photoresist film is exposed.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority from Japanese patent applicationNo. 2005-197938 filed on Jul. 6, 2005, the content of which is herebyincorporated by reference into this application.

BACKGROUND OF THE INVENTION

The present invention relates to a manufacturing technology of asemiconductor integrated circuit device, in particular, a technologyeffective when applied to the formation of interconnects using the dualdamascene process.

In recent years, a fine-pitch interconnect forming method calleddamascene process is becoming a leading method in the manufacture of aminiaturized semiconductor integrated circuit device.

The damascene process involves forming a fine interconnect trench in aninterlayer insulating film over a semiconductor substrate, depositing ametal film over the interlayer insulating film including the inside ofthis interconnect trench, removing the metal film outside theinterconnect trench by chemical mechanical polishing and forming aminute embedded interconnect in the interconnect trench.

A process called “dual damascene process” is the above-describeddamascene process but has less steps. It involves the steps of forming,below an interconnect trench formed in an interlayer insulating film, avia hole to be connected to a lower-level interconnect andsimultaneously filling a metal film in the interconnect trench and viahole to form an interconnect. A process of forming a metal plug in a viahole in advance and then forming an embedded interconnect in theinterconnect trench is called single damascene process.

As a metal material for an embedded interconnect, Cu (copper) istypically employed because reliability is not impaired even by theformation of fine interconnects. When an embedded interconnect is formedin an interlayer insulating film by the damascene process, it is thecommon practice to make the interlayer insulating film from alow-dielectric insulating material in order to reduce the capacitancegenerated between two adjacent interconnects. A technology of forming anembedded interconnect in an interlayer insulating film made of alow-dielectric material by the damascene process is described, forexample, in Japanese Unexamined Patent Publication No. 2004-221275 orJapanese Unexamined Patent Publication No. 2003-124307.

In Japanese Unexamined Patent Publication No. 2003-163265, disclosed isa manufacturing method of an interconnect layer by the single damasceneprocess, which comprises using an SiCN film as an antireflective film ofa resist pattern for the formation of a via hole.

SUMMARY OF THE INVENTION

The outline of the formation steps of a multilevel Cu interconnect bythe dual damascene process which were investigated by the presentinventors will next be described.

(Step 1) A semiconductor element is formed over a semiconductorsubstrate and a lower-level interconnect is formed over thesemiconductor element in accordance with the conventionally knownprocess.

(Step 2) After deposition of an interlayer insulating film over thelower-level interconnect and formation of an antireflective film overthe interlayer insulating film, a photoresist film is formed over theantireflective film. The photoresist film is a film to which a patternhaving a via hole formation region opened therein has been transferredby exposure with a photomask having a via hole pattern formed thereinand then development. The antireflective film is formed in order toprevent the reduction of the resolution upon exposure of the photoresistfilm, which will otherwise occur by the exposure light reflected fromthe surface of the lower-level interconnect and incident on thephotoresist film. The antireflective film formed below the photoresistfilm is also called BARC (bottom anti-reflective coating).(Step 3) With the photoresist film as a mask, the antireflective filmand interlayer insulating film are dry etched to form a via hole in theinterlayer insulating film. Then, the photoresist film andantireflective film are removed and a filler is filled in the via hole.The filler is made of an insulating material having a substantiallysimilar composition to that of the antireflective film. The filler isfilled in the via hole in the following manner. The filler is depositedover the interlayer insulating film including the inside of the via holeand then the filler outside the via hole is removed by etch back. Bythis etch back, the surface of the filler filled in the via hole becomesalmost flat and becomes on the substantially same level as the surfaceof the interlayer insulating film.(Step 4) A second antireflective film is formed over the interlayerinsulating film and over this antireflective film, a second photoresistfilm is formed. This second photoresist film is a film to which apattern having an interconnect trench region opened therein has beentransferred by exposure with a photomask having an interconnect trenchpattern formed therein and then development. With the second photoresistfilm as a mask, the second antireflective film is dry etched and then,the interlayer insulating film is dry etched while leaving a lowerportion thereof without etching, whereby an interconnect trench isformed over the via hole.(Step 5) After removal of the second photoresist film, the secondantireflective film is also removed. When the second antireflective filmis removed, the filler filled in the via hole is also removed to exposethe surface of the lower-level interconnect from the bottom of the viahole. A Cu interconnect is then formed in the interconnect trench andvia hole. The Cu interconnect is formed by depositing a Cu film over theinterlayer insulating film including the insides of the interconnecttrench and via hole by sputtering or plating and then removing the Cufilm outside of the interconnect trench by chemical mechanicalpolishing. A multilevel Cu interconnect is formed over the semiconductorsubstrate by repeating the above-described Steps 2 to 5.

In the multilevel Cu interconnect formed over a semiconductor substrate,an upper-level interconnect usually has greater width and thickness.Accordingly a via hole formed in an upper interlayer insulating film hasgreater diameter and depth than a via hole formed in a lower interlayerinsulating film.

When a via hole has greater diameter and depth, however, it becomesdifficult to completely fill a filler in the via hole in theabove-described Step 3. As a result, when after deposition of a fillerover an interlayer insulating film including the inside of a via hole,the filler outside of the via hole is removed by etch back, the surfaceof the filler filled in the via hole does not become flat and thereappears a difference between the surface of the filler and the surfaceof the interlayer insulating film, leading to a problem that in Step 4,an antireflective film cannot be formed uniformly over the interlayerinsulating film.

An object of the present invention is to provide a technology of forminga multilevel Cu interconnect in a high yield by the dual damasceneprocess.

Another object of the present invention is to provide a technologycapable of simplifying the formation step of a multilevel Cuinterconnect by the dual damascene process.

The above-described and other objects and novel features of the presentinvention will be apparent in the description herein and accompanyingdrawings.

The outline of typical inventions, of the inventions disclosed by thepresent application, will next be described briefly.

A manufacturing method of a semiconductor integrated circuit device ofthe present invention comprises the steps of: (a) forming asemiconductor element over the main surface of a semiconductor substrateand forming a first-level interconnect composed of one or more layersover the semiconductor element; (b) forming a first interlayerinsulating film over the first-level interconnect and forming a firststopper film in a portion of the first interlayer insulating film, (c)forming a first antireflective film over the first interlayer insulatingfilm and forming a first photoresist film over the first antireflectivefilm, (d) etching the first antireflective film, the first interlayerinsulating film and first stopper film with the first photoresist filmas a mask to form a first via hole in the first interlayer insultingfilm, (e) removing the first photoresist film and first antireflectivefilm and then filling a first filler in the first via hole, (f) afterthe step (e), forming a second photoresist film over the firstinterlayer insulating film without using an antireflective film, (g)removing, by etching with the second photoresist film as a mask, thefirst interlayer insulating film from a region including a region inwhich the first via hole has been formed, thereby forming a firstinterconnect trench in the first interlayer insulating film over thefirst stopper film, and (h) removing the second photoresist film andfirst filler and then filling a metal film in the first interconnecttrench and first via hole to form a second-level interconnect, whereinthe first stopper film is made of a material having a low opticalreflectance so as to use it as an antireflective film when the secondphotoresist film formed over the first interlayer insulating film isexposed to transfer a pattern of the first interconnect trench to thesecond photoresist film.

Advantages available by the typical inventions, of the inventionsdisclosed by the present application, will next be described briefly.

The present invention enables to form a multilevel Cu interconnect in ahigh yield by the dual damascene process. In addition, the inventionenables to simplify the dual damascene formation step of a multilevel Cuinterconnect.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary cross-sectional view of a semiconductorsubstrate illustrating a manufacturing step of a semiconductorintegrated circuit device according to one embodiment of the presentinvention.

FIG. 2 is a fragmentary cross-sectional view of a semiconductorsubstrate illustrating a manufacturing step of a semiconductorintegrated circuit device following that of FIG. 1.

FIG. 3 is a fragmentary cross-sectional view of a semiconductorsubstrate illustrating a manufacturing step of a semiconductorintegrated circuit device following that of FIG. 2.

FIG. 4 is a fragmentary cross-sectional view of a semiconductorsubstrate illustrating a manufacturing step of a semiconductorintegrated circuit device following that of FIG. 3.

FIG. 5 is a fragmentary cross-sectional view of a semiconductorsubstrate illustrating a manufacturing step of a semiconductorintegrated circuit device following that of FIG. 4.

FIG. 6 is a fragmentary cross-sectional view of a semiconductorsubstrate illustrating a manufacturing step of a semiconductorintegrated circuit device following that of FIG. 5.

FIG. 7 is a fragmentary cross-sectional view of a semiconductorsubstrate illustrating a manufacturing step of a semiconductorintegrated circuit device following that of FIG. 6.

FIG. 8 is a fragmentary cross-sectional view of a semiconductorsubstrate illustrating a manufacturing step of a semiconductorintegrated circuit device following that of FIG. 7.

FIG. 9 is a fragmentary cross-sectional view of a semiconductorsubstrate illustrating a manufacturing step of a semiconductorintegrated circuit device following that of FIG. 8.

FIG. 10 is a fragmentary cross-sectional view of a semiconductorsubstrate illustrating a manufacturing step of a semiconductorintegrated circuit device following that of FIG. 9.

FIG. 11 is a fragmentary cross-sectional view of a semiconductorsubstrate illustrating a manufacturing step of a semiconductorintegrated circuit device following that of FIG. 10.

FIG. 12 is a fragmentary cross-sectional view of a semiconductorsubstrate illustrating a manufacturing step of a semiconductorintegrated circuit device following that of FIG. 11.

FIG. 13 is a fragmentary cross-sectional view of a semiconductorsubstrate illustrating a manufacturing step of a semiconductorintegrated circuit device following that of FIG. 12.

FIG. 14 is a fragmentary cross-sectional view of a semiconductorsubstrate illustrating a manufacturing step of a semiconductorintegrated circuit device following that of FIG. 13.

FIG. 15 is a fragmentary cross-sectional view of a semiconductorsubstrate illustrating a manufacturing step of a semiconductorintegrated circuit device following that of FIG. 14.

FIG. 16 is a fragmentary cross-sectional view of a semiconductorsubstrate illustrating a manufacturing step of a semiconductorintegrated circuit device following that of FIG. 15.

FIG. 17 is a fragmentary cross-sectional view of a semiconductorsubstrate illustrating a manufacturing step of a semiconductorintegrated circuit device following that of FIG. 16.

FIG. 18 is a fragmentary cross-sectional view of a semiconductorsubstrate illustrating a manufacturing step of a semiconductorintegrated circuit device following that of FIG. 17.

FIG. 19 is a fragmentary cross-sectional view of a semiconductorsubstrate illustrating a manufacturing step of a semiconductorintegrated circuit device following that of FIG. 18.

FIG. 20 is a fragmentary cross-sectional view of a semiconductorsubstrate illustrating a manufacturing step of a semiconductorintegrated circuit device following that of FIG. 19.

FIG. 21 is a fragmentary cross-sectional view of a semiconductorsubstrate illustrating a manufacturing step of a semiconductorintegrated circuit device following that of FIG. 20.

FIG. 22 is a fragmentary cross-sectional view of a semiconductorsubstrate illustrating a manufacturing step of a semiconductorintegrated circuit device following that of FIG. 21.

FIG. 23 is a fragmentary cross-sectional view of a semiconductorsubstrate illustrating a manufacturing step of a semiconductorintegrated circuit device following that of FIG. 22.

FIG. 24 is a fragmentary cross-sectional view of a semiconductorsubstrate illustrating a manufacturing step of a semiconductorintegrated circuit device following that of FIG. 23.

FIG. 25 is a fragmentary cross-sectional view of a semiconductorsubstrate illustrating a manufacturing step of a semiconductorintegrated circuit device following that of FIG. 24.

FIG. 26 is a fragmentary cross-sectional view of a semiconductorsubstrate illustrating a manufacturing step of a semiconductorintegrated circuit device following that of FIG. 25.

FIG. 27 is a fragmentary cross-sectional view of a semiconductorsubstrate illustrating a manufacturing step of a semiconductorintegrated circuit device according to another embodiment of the presentinvention.

FIG. 28 is a fragmentary cross-sectional view of a semiconductorsubstrate illustrating a manufacturing step of a semiconductorintegrated circuit device following that of FIG. 27.

FIG. 29 is a fragmentary cross-sectional view of a semiconductorsubstrate illustrating a manufacturing step of a semiconductorintegrated circuit device following that of FIG. 28.

FIG. 30 is a fragmentary cross-sectional view of a semiconductorsubstrate illustrating a manufacturing step of a semiconductorintegrated circuit device following that of FIG. 29.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will hereinafter be describedspecifically based on accompanying drawings. In all the drawings fordescribing the below-described embodiments, members having like functionwill be identified by like reference numerals and overlappingdescriptions will be omitted.

Embodiment 1

A semiconductor integrated circuit device having, for example, afour-layer Cu interconnect and fuse will be described in thisEmbodiment. A manufacturing method of it will next be described in theorder of steps referring to FIGS. 1 to 26.

As illustrated in FIG. 1, an n channel MISFET (Qn) and a p channelMISFET (Qp) are formed as semiconductor elements over the main surfaceof a semiconductor substrate (which will hereinafter be called“substrate” simply), for example, made of single crystal silicon. Inthis drawing, indicated at numerals 2, 4 and 5 are element isolationtrench, p well and n well, respectively.

The element isolation trench 2 is formed by filling an insulating film,for example, a silicon oxide film 3 in a trench formed by etching thesubstrate 1. The p well 4 and n well 5 are formed by ion-implanting ptype impurity (boron) and n type impurity (phosphorus) into thesubstrate 1 and heat treating the substrate 1 to diffuse theseimpurities into the substrate 1.

The n channel MISFET (Qn) is composed of a gate insulating film 6 madeof a silicon oxide film or silicon oxynitride film formed over thesurface of the p well 4, a gate electrode 7 made of, for example, apolycrystalline silicon film formed over the gate insulating film 6,sidewall spacers 8 made of, for example, a silicon oxide film formedover side surfaces of the gate electrode 7, a pair of n typesemiconductor regions (source and drain) 11 formed in the p well 4 onboth sides of the gate electrode 7 and the like. The p channel MISFET(Qp) is composed of the gate insulating film 6, gate electrode 7,sidewall spacers 8, a pair of p type semiconductor regions (source anddrain) 12 formed in the n well 5 on both sides of the gate electrode 7and the like. In the polycrystalline film constituting the gateelectrode 7 of the n channel MISFET (Qn), an n type impurity(phosphorus) is introduced, while a p type impurity (boron) isintroduced into the polycrystalline film constituting the gate electrode7 of the p channel MISFET (Qp). Over the respective surfaces of the gateelectrode 7 and n type semiconductor regions (source and drain) 11 ofthe n channel MISFET (Qn) and the respective surfaces of the gateelectrode 7 and p type semiconductor regions (source and drain) 12 ofthe p channel MISFET (Qp), a Co (cobalt) silicide film 9 is formed forthe purpose of reducing the resistance of each of the gate electrode 7and source and drain.

As illustrated in FIG. 2, a plug 16 and a first-level interconnect 19are formed over the n channel MISFET (Qn) and p channel MISFET (Qp) andthe n channel MISFET (Qn) and p channel MISFET (Qp) are electricallyconnected to the first-level interconnect 19 via the plug 16.

The first-level interconnect 19 is formed in the following manner.First, after deposition of an etching stopper film 13 and an insulatingfilm 14 over the substrate 1, the surface of the insulating film 14 isplanarized by chemical mechanical polishing. The etching stopper film 13is made of, for example, a silicon nitride film deposited by CVD, whilethe insulating film 14 is made of, for example, a silicon oxide filmdeposited by CVD.

Then, the insulating film 14 over each of the n type semiconductorregions (source and drain) 11 of the n channel MISFET (Qn) and p typesemiconductor regions (source and drain) 12 of the p channel MISFET (Qp)is etched, followed by etching of the etching stopper film 13 below theresulting insulating film 14 to form a contact hole 15. A plug 16 isthen formed inside of the contact hole 15. The plug 16 is made of, forexample, a film stack of a TiN (titanium nitride) film and a W(tungsten) film. The TiN film functions as a barrier metal film of the Wfilm. The barrier metal film may be made of a film stack of a TiN filmand a Ti (titanium) film.

After deposition of an insulating film 17 (SiOC film 17) of about 200 nmthick and an insulating film 18 of about 50 nm thick made of a siliconoxide film over the insulating film 14 by CVD, the insulating film 18and SiOC film 17 are dry etched with a photoresist film (notillustrated) as a mask to form an interconnect trench 20. The insulatingfilm 17 (SiOC film 17) is a low dielectric insulating film for reducingthe interconnect capacitance and is, for example, an insulating filmhaving a dielectric constant lower than that of a silicon oxide film(for example, TEOS (tetraethoxysilane) oxide film). In general, a film,such as TEOS film, having a specific dielectric constant ∈ as low asabout 4.1 to 4.2 or less is called a low dielectric insulating film. Inthis embodiment, the specific dielectric constant is about 2.7. Theinsulating film 18 formed over the SiOC film 17 functions as aprotective film for preventing deterioration of the SiOC film 17 havinga low mechanical strength which will otherwise occur by chemicalmechanical polishing.

A barrier metal film of about 50 nm thick made of a TiN film or a filmstack of a TiN film and a Ti film is deposited inside of theinterconnect trench 20 by sputtering and then a thick (from about 800 nmto 1600 nm) Cu film capable of completely filling therewith the insideof the interconnect trench 20 is deposited by sputtering or plating. Thebarrier metal film functions as a film for preventing diffusion of theCu film in the surrounding insulating film. In addition to the TiN film,various conductive films which hardly react with Cu, for example, metalnitride films such as WN (tungsten nitride) film and TaN (tantalumnitride) film, alloy films obtained by adding Si to such metal nitridefilms, refractory metal films such as Ta film, Ti film, W film and TiWfilm, and film stacks of these refractory metal films are usable as thebarrier metal film.

The cu film and barrier metal film outside the interconnect trench 20are removed by chemical mechanical polishing, whereby a metal filmcomposed mainly of Cu is embedded inside of the interconnect trench 20.In such a manner, a first-level interconnect 19 is made of a film stackof the barrier metal film and Cu film remaining inside of theinterconnect trench 20.

As illustrated in FIG. 3, barrier insulating films 21 and 22, interlayerinsulating film 23 and insulating film 24 are deposited successivelyover the first-level interconnect 19. The barrier insulating film 21 isan insulating film for preventing the diffusion of Cu, which is amaterial of the first-level interconnect 19, into the interlayerinsulating film 23 and it is made of, for example, an SiCN film having athickness of from about 20 nm to 100 nm and deposited, for example, byplasma CVD. The barrier insulating film 22 is an insulating film forpreventing the diffusion, into the interlayer insulating film 21, of anamine compound contained in the SiCN film constituting the underlyingbarrier insulating film 21 and it is made of, for example, an SiCO filmof from about 10 nm to 100 nm thick deposited by CVD. The diffusion ofthe amine compound into the interlayer insulating film 23 causes furtherdiffusion of it into a photoresist film formed over the insulating film23 in the subsequent step, which may deactivate the photosensitivefunction of the photoresist film.

The interlayer insulating film 23 is made of a low dielectric insulatingfilm, for example, the above-described SiOC film in order to reduce thecapacitance formed between the first-level interconnect 29 and asecond-level interconnect which will be formed in the later step. TheSiOC film is deposited by CVD and its thickness is about 460 nm. Alow-dielectric film such as the interlayer insulating film 23 can alsobe formed by the application method. The insulating film 24 formed overthe interlayer insulating film 23 is, similar to the lower insulatingfilm 18, an insulating film for protecting the interlayer insulatingfilm 23 made of an SiOC film having a low mechanical strength when a Cuinterconnect is formed by chemical mechanical polishing. It is made of,for example, a silicon oxide film of about 50 nm thick deposited by CVD.

As illustrated in FIG. 4, an antireflective film 25 is formed over theinsulating film 24, followed by the formation of a photoresist film 26over the antireflective film 25. When the photoresist film 26 is formed,exposure light reflected from the surface of the first-levelinterconnect 19 is incident on the photoresist film 26 and deterioratesthe resolution. The antireflective film 25 is formed for preventing suchdeterioration in the resolution. The antireflective film is a filmcalled “BARC (bottom anti-reflective coating)” and having a highrefractive index than that of the underlying insulating film 24 andinterlayer insulating film 23. The photoresist film 26 is a film towhich a pattern having an opening corresponding to a via hole formationregion has been transferred by the exposure through a photomask (notillustrated) having a via hole pattern formed therein and thendevelopment.

As illustrated in FIG. 5, the antireflective film 25, insulating film 24and interlayer insulating film 23 are dry-etched successively with thephotoresist film 26 as a mask, whereby a via hole 27 is formed over thefirst-level interconnect 19.

Then, the photoresist film 26 and antireflective film 25 are removed.When the antireflective film 25 is made of the above-described BARC, ithas a composition similar to that of the photoresist film 26 so that thephotoresist film 26 and antireflective film 25 can be removedsimultaneously by washing once. As illustrated in FIG. 6, a filler 28 isfilled inside of the via hole 27. The filler 28 is made of an insulatingmaterial having almost a similar composition to that of theantireflective film 25. The filler 28 is filled by spin coating thefiller 28 on the insulating film 24 including the inside of the via hole27, curing it and then, removing the filler 28 outside the via hole 27by etch back. The diameter of the via hole 27 for connecting thefirst-level interconnect 19 to a second-level interconnect to be formedlater is relatively small so that by employing this etch back, thefiller 28 filled in the via hole 27 has almost a flat surface and at thesame time, its surface is almost on the same level as that of theinsulating film 24.

As illustrated in FIG. 7, an antireflective film 30 is formed over theinsulating film 24 and then, a photoresist film 31 is formed over theantireflective film 30. In this Embodiment, the above-described BARC isused as the antireflective film 30. The photoresist film 31 is a film towhich a pattern having therein an opening of an interconnect trenchformation region has been transferred by the exposure and thendevelopment through a photomask (not illustrated) having an interconnecttrench pattern formed therein.

As illustrated in FIG. 8, the antireflective film 30 and insulating film24 are dry etched successively with the photoresist film 31 as a mask,followed by dry etching of the interlayer insulating film 23 whileleaving a lower portion thereof without etching, whereby an interconnecttrench 23 is formed. The interlayer insulating film 23 has no filmserving as an etching stopper so that the interconnect trench 23 isformed while controlling the etching time. Formation of a film having ahigher dielectric constant than that of the interlayer insulating film23 inevitably increases an interconnect capacitance because the size ofa lower-level interconnect is designed to be finer than that of anupper-level interconnect. In this Embodiment, the interconnectcapacitance can be reduced by not forming an etching stopper film in theinterlayer insulating film 23. In addition, since the interconnecttrench in the lower layer is designed to have a shallower depth thanthat of the interconnect trench in the upper layer, an etching amountfor the formation of the interconnect trench can be reduced. The filmthickness can therefore be adjusted by controlling an etching timewithout disposing an etching stopper film in particular.

After removal of the photoresist film 31, the antireflective film 30over the insulating film 24 is removed by dry etching as illustrated inFIG. 9. The filler 28 filled in the via hole 27 and barrier insulatingfilms 22 and 21 which lie therebelow are etched simultaneously to exposethe surface or the first-level interconnect 19 from the bottom of thevia hole 27.

As illustrated in FIG. 10, a second-level interconnect 33 is then formedinside of the interconnect trench 32 and via hole 27. The second-levelinterconnect 33 is formed by depositing, by sputtering, a thin TiN film(barrier metal film) having a thickness of about 50 nm over theinsulating film 24 including the inside of the interconnect trench 32and via hole 27. A thick Cu film for filling therewith the interconnecttrench 32 and via hole 27 is then deposited over this TiN film bysputtering or plating, followed by removal of the Cu film and barriermetal film existing outside the interconnect trench 32 by chemicalmechanical polishing. The insulating film 24 has stronger mechanicalstrength than the interlayer insulating film 23 so that it serves as aprotective film of the interlayer insulating film 23.

As illustrated in FIG. 11, after deposition of the barrier insulatingfilm 34, interlayer insulating film 35 and antireflective film 36 overthe second-level interconnect 33, the antireflective film 36 andinterlayer insulting film 35 are dry etched with the photoresist film 37formed over the antireflective film as a mask, whereby a via hole 38 isformed over the second-level interconnect 33.

The barrier insulating film 34 is, similar to the barrier insulatingfilm 21 for covering therewith the surface of the first-levelinterconnect 19, an insulating film for preventing the diffusion of Cu,which is an interconnect material, in the interlayer insulating film 35and it is made of an SiCN film of about from 20 nm to 100 nm thickdeposited, for example, by plasma CVD.

In a multilevel interconnect formed over the substrate 1, aninterconnect capacitance of an upper-level interconnect becomes smallerthat of a lower-level one because the distance between two adjacentinterconnects is wider in the upper-level interconnect. When thecapacitance between two third-level interconnects which will be formedlater or between the third-level interconnect and the second-levelinterconnect is not an important factor, the interlayer insulating film35 is made of a silicon oxide film of about 700 nm thick deposited, forexample, by CVD. Since a silicon oxide film has a denser film qualitythan an SiCO film which is a low dielectric material, diffusion of anamine compound does not become a problem even when the interlayerinsulating film 35 made of a silicon oxide film is deposited directlyover the barrier insulating film 34 made of an SiCN film. Since the SiCNfilm has comparatively low adhesion to a silicon oxide film, theadhesion between the barrier insulating film 34 and the interlayerinsulating film 35 may be improved by forming an SiCO film therebetween.As a silicon oxide series material constituting the interlayerinsulating film 35, silicon oxide added with F (fluorine) for reducingits dielectric constant may be used.

When a capacitance between two third-level interconnects (43) or betweenthe third-level interconnect and the second-level interconnect is animportant factor, on the other hand, the interlayer insulating film 35is made of a low dielectric material such as SiCO film. In this case, itis desired to form an SiCO film between the barrier insulating film 34and the interlayer insulating film 35 to prevent the diffusion of anamine compound in the barrier insulating film 34. In the belowdescription, the interlayer insulating film 35 is made of a siliconoxide film.

After removal of the photoresist film 37 and antireflective film 36, afiller 39 is filled in the via hole 38 as illustrated in FIG. 12. Asdescribed above, the filler 39 is made of an insulating material havingalmost a similar composition to that of the above-describedantireflective film. The filling method of the filler 39 is also similarto that employed for filling the filler 28 in the via hole 27. Since thediameter of a via hole 38 for connecting the second-level interconnect33 to a third-level interconnect which will be formed later isrelatively small, the surface of the filler 39 filled in the via hole 38is almost flat and at the same time is on the same level with thesurface of the interlayer insulating film 35.

As illustrated in FIG. 13, an interconnect trench 42 is formed in theinterlayer insulating film 35. The interconnect trench 35 is formed byforming an antireflective film 40 over the interlayer insulating film35, forming a photoresist film 41 over the antireflective film 40, dryetching the antireflective film 40 with the photoresist film 41 as amask and then, dry etching the interlayer insulating film 35 whileleaving a lower portion thereof without etching. In this Embodiment, theinterconnect trench 42 is formed by time-controlled etching similar tothat employed for the formation for the interconnect trench 32.

As illustrated in FIG. 14, a third-level interconnect 43 is formed inthe interconnect trench 42 and via hole 38. The third-level interconnect43 is formed by removing the photoresist film 41 and then removing theantireflective film 40 by dry etching. The antireflective film 40 isremoved by removing the filler 39 filled in the via hole 38 and theunderlying barrier insulating film 34 to expose the surface of thesecond-level interconnect 33 from the bottom of the via hole 38. Overthe interlayer insulating film 35 including the inside of theinterconnect trench 42 and via hole 38, a thin TiN film (barrier metalfilm) is deposited by sputtering. After deposition of a thick Cu filmover the TiN film by sputtering or plating, the Cu film and barriermetal film outside the interconnect trench 42 are removed by chemicalmechanical polishing.

As illustrated in FIG. 15, a barrier insulating film 44 and aninterlayer insulating film 45 are deposited over the third-levelinterconnect 43. The barrier insulating film 44 is an insulating filmfor preventing diffusion of Cu and similar to the underlying barrierinsulating films 34 and 21, it is made of an SiCN film of about from 50nm to 100 nm deposited by the plasma CVD. In a fourth-level interconnectto be formed in the interlayer insulating film 45 in the subsequentstep, the size of each interconnect, distance between interconnects andthickness of each interconnect are greater than those of the lower-levelinterconnects. The interlayer insulating film 45 is therefore made of asilicon oxide film of about 1 μm thick deposited by CVD. An SiCO filmmay be formed between the barrier insulating film 44 and interlayerinsulating film 45 for the purpose of improving the adhesiontherebetween. As a silicon oxide series material constituting theinterlayer insulating film 45, silicon oxide added with F to reduce itsdielectric constant may be used.

When an interconnect trench is formed by etching the interlayerinsulating film 45 while leaving a lower portion thereof withoutetching, the interlayer insulating film 45 having a great thicknessmakes it difficult to control the depth of the interconnect trench withhigh precision. Described specifically, the interconnect trenches 52 and53 are deeper than the above-described interconnect trenches 32 and 42so that they cannot be formed easily by time-controlled etching employedfor the formation of the interconnect trenches 32 and 43. The depth ofthe interconnect trench is therefore controlled by forming, in theinterlayer insulating film 45, a stopper film 46 having an etchselectivity different from that of the interlayer insulating film 45 andstopping etching at the surface of the stopper film 46. In thisEmbodiment, an SiCN film of from about 10 nm to 100 nm thick depositedby plasma CVD is used as the stopper film 46 formed in the interlayerinsulting film 45. The SiCN film has a high etch selectivity relative toa silicon oxide film and has a low dielectric constant so that it isuseful as the stopper film 46. It also has a lower optical reflectance(has a smaller refractive index) than that of the interlayer insulatingfilm 45 so that it also functions as an antireflective film as will bedescribed later.

As illustrated in FIG. 16, after formation of an antireflective film 47over the interlayer insulating film 45, the antireflective film 47,interlayer insulating film 45, stopper film 46 and interlayer insulatingfilm 45 are dry-etched successively with the photoresist film 48 formedover the antireflective film 47 as a mask, whereby a via hole 38 isformed over the third-level interconnect 43.

After removal of the photoresist film 48 and antireflective film 47, afiller 50 is filled in the via hole 49 as illustrated in FIG. 17. Thematerial and filling method of the filler 50 are similar to thosedescribed above. The via hole 49 for the formation of a fourth-levelinterconnect has larger diameter and depth than the underlying via holes38 and 27, which prevents complete filling of the filler 50.Accordingly, the filler 50 filled in the via hole 49 does not have aflat surface and it inevitably has a step difference with the surface ofthe interlayer insulating film 45.

As illustrated in FIG. 18, a photoresist film 51 is formed over theinterlayer insulating film 45. As described above, the filler 50 filledin the via hole 49 does not have a flat surface and has a stepdifference with the surface of the interlayer insulating film 45 so thatit is difficult to apply a uniformly thick antireflective film over theentire surface of the interlayer insulating film 45. Accordingly, aphotoresist film 51 is directly formed over the interlayer insulatingfilm 45 without using the antireflective film.

The photoresist film 51 is a film to which a pattern having aninterconnect trench formation region and a fuse formation region openedtherein has been transferred by the exposure through a photomask (notillustrated) having an interconnect trench pattern and a fuse patternformed therein and then development. As described above, since thestopper film 46 made of an SiCN film having a low optical reflectance isformed in the interlayer insulating film 45, it is possible to preventthe inconvenience such as deterioration of resolution, which willotherwise occur by the exposure light reflecting from the surface of thethird-level interconnect 43 and incident on the photoresist film 51,without forming an antireflective film below the photoresist film 51. Astep of forming an antireflective film below the photoresist film 51 istherefore unnecessary, leading to a simplification of the manufacturingprocess. The stopper film 46 formed in the interlayer insulating film 45is required to have an etch selectivity different from that of a siliconoxide film, a low optical reflectance and a low dielectric constant.Examples of such an insulating material include, in addition to theabove-described SiCN, silicon nitride (SiN) and silicon oxynitride(SiON). Of these, SiCN is most preferred.

As illustrated in FIG. 19, with the photoresist film 51 as a mask, theinterlayer insulating film 45 is dry etched and etching is stopped atthe surface of the stopper film 46, whereby interconnect trenches 52 and53 are formed in the interlayer insulating film 45 over the stopper film46.

After removal of the photoresist film 51, the filler 50 filled in thevia hole 49 is removed by dry etching to expose the surface of thethird-level interconnect 43 from the bottom of the via hole 49 asillustrated in FIG. 20.

As illustrated in FIG. 21, a fourth-level interconnect 54 is formedinside of the interconnect trench 52 and via hole 49, while thefourth-level interconnect 54 which will be a fuse 55 is formed inside ofthe interconnect trench 53. Although not illustrated in this drawing,the fuse 55 is connected to a resistor via a lower-level interconnect.The resistor is formed by the polycrystalline silicon film constitutingthe layer of the gate electrode 7 of the MISFETs (Qn and Qp). When aprobe test, which will be described later, finds some defects in aportion of a CMOS memory, the fuse 55 is cut by using a laser beam orthe like to change a resistance of the resistor and a redundant memoryis replaced for the defective memory.

The fourth-level interconnect 54 and fuse 55 are formed by depositing athin TiN film (barrier metal film) over the interlayer insulating film45 including the insides of the interconnect trenches 52 and 53, and viahole 49 by sputtering, depositing a thick Cu film over the TiN film bysputtering or plating and then removing the Cu film and barrier metalfilm outside the interconnect trenches 52 and 53 by chemical mechanicalpolishing.

The etching stopper film 46 remains in the interlayer insulating film45, but the distance between two adjacent interconnects is greater inthe four-level interconnect than that in the underlying first-level,second-level or third-level interconnect and the interlayer insulatingfilm 45 has a greater film thickness so that an increase in thecapacitance between interconnects and capacitance between interconnectlayers can be neglected substantially.

As illustrated in FIG. 22, a barrier insulating film 56 and aninterlayer insulating film 57 are deposited over the fourth-levelinterconnect 54 and fuse 55. The barrier insulating film 56 is aninsulating film for preventing the diffusion of Cu and similar to theunderlying barrier insulating films 44, 34 and 21, it is made of an SiCNfilm deposited by plasma CVD. The interlayer insulating film 57 is,similar to the underlying interlayer insulating films 45 and 32, made ofa silicon oxide series insulating film having a thickness of about 900nm. In FIG. 22 and the drawings after FIG. 22, portions lying below thefourth-level interconnect 54 are omitted.

As described later, an interlayer insulating film and surface protectivefilm are formed over the fourth-level interconnect 54 and fuse 55. Inthe interlayer insulating film and surface protective film over the fuse55, an opening for exposing the fuse 55 to laser beam is formed. Ifwater enters from outside into the circuit via this opening, the fuse 55may presumably be corroded. In this Embodiment 1, the thickness of thebarrier insulating film 56 (for example, from about 150 nm to 200 nm) ismade greater than that of the underlying barrier insulating films 44, 34and 21 to improve the moisture resistance of the fuse 55.

As illustrated in FIG. 23, an uppermost-level interconnect (fifth-levelinterconnect) 60 is formed over the interlayer insulating film 57,followed by the formation of a surface protective film 61 over theuppermost-level interconnect 60. The uppermost-level interconnect 60 isformed in the following manner. With a photoresist film as a mask, theinterlayer insulating film 57 over the fourth-level interconnect 54 isdry etched and then, the barrier insulating film 56 which lie below theinterlayer insulating film 57 is dry etched to form a through-hole 58. Aplug 59 is formed inside of the through-hole 58. The plug 59 is, similarto the plug 16 of the lower layer, made of a film stack of a TiN filmand W film. Over the interlayer insulating film 57, a TiN of from about50 nm to 100 nm, an Al (aluminum) alloy film of about 1 μm thick and aTiN film of from about 50 nm to 100 nm thick is deposited by sputtering.With a photoresist film (not illustrated) as a mask, these conductivefilms are etched to form the uppermost-level interconnect 60. Thesurface protective film 61 over the uppermost-level interconnect 60 ismade of a film stack of a silicon oxide film of about 200 nm thick and asilicon nitride film of about 600 nm thick deposited by plasma CVD.

As illustrated in FIG. 24, with a photoresist film (not illustrated) asa mask, the surface protective film 61 is dry etched to expose a portionof the uppermost-level interconnect 60, whereby a bonding pad 60B isformed. The surface protective film 61 and interlayer insulating film 57over the fuse 55 are dry etched to form an opening 62. During theformation of this opening, the barrier insulating film 55 is left overthe fuse 55 by terminating the etching at the surface of the barrierinsulating film 56 which covers therewith the fuse 55.

Since the barrier insulating film 55 over the fuse 55 is thicker thanthe underlying barrier insulating film 44, 34 or 21, the moistureresistance can be maintained. Described specifically, supposing that thethickness of the barrier insulating film 56 is equal to that of thebarrier insulating film 44, 34 or 21, the barrier insulating filmbecomes thin further, for example, by the etching step for the formationof the opening 62 over the fuse 55, oxygen plasma ashing step for theremoval of the photoresist film, washing step or the like step, whichdisadvantageously leads to lowering in moisture resistance. Particularlyin etching of the opening 62, a film thicker than the underlyinginterlayer insulating film must be etched so that there is a fear of thebarrier insulating film 56 becoming excessively thin by overetching. Itis therefore necessary to form the barrier insulating film 56 with athickness greater than that of the underlying barrier insulating film44, 34 or 21.

An electrical test of the circuit (probe test) is carried out whileapplying a probe (not illustrated) onto the surface of the bonding pad60B. When the probe test reveals the existence of a defect in a portionof the semiconductor device, the fuse 55 is exposed to a laser beam viathe opening 62 to cut the fuse 55, whereby the defective memory issubstituted by a redundant memory.

The insulating film left over the fuse 55 has an enough thickness to becut by exposure to a laser beam which will be described later. Theinsulating film 57 may be left as needed.

As illustrated in FIG. 25, after deposition of a polyimide resin film 63over the surface protective film 61, a leading-out interconnect 64 isformed over the polyimide resin film 63, whereby the bonding pad 60B andleading-out interconnect 64 are electrically connected. This leading-outinterconnect 64 is an interconnect for electrically connecting a solderbump constituting an external connection terminal of a CMOS memory tothe bonding pad 60B. The leading-out interconnect 64 is formed bydepositing the polyimide resin film 63 over the surface protective film61, and etching the polyimide resin film 63 over the bonding pad 60Bwith a photoresist film (not illustrated) as a mask to expose thesurface of the bonding pad 60B. Then, after formation of a photoresistfilm (not illustrated) having the formation region of the leading-outinterconnect 64 opened therein over the surface protective film 61, a Cufilm is deposited over the surface protective film 61 by plating orsputtering.

As illustrated in FIG. 26, the surface of the leading-out interconnect64 made of the Cu film is covered with a polyimide resin film 65 andthen, a portion of the polyimide resin film 65 is etched to expose oneend of the leading-out interconnect 64. An Au (gold) film 66 is formedon the surface thereof by plating. A solder bump 67 is then formed onthe surface of the Au (gold) film 66 by the printing method, whereby theexternal connection terminal of the semiconductor integrated circuitdevice is formed.

During the formation step of the leading-out interconnect 64, thebarrier insulating film 56 over the fuse 55 is thinned by etching orashing of the photoresist film, but it is possible to prevent thedeterioration of moisture resistance by thickening the barrierinsulating film 56 in advance.

Embodiment 2

In Embodiment 1, an interconnect trench was formed after formation of avia hole in an interlayer insulating film. In this Embodiment, on theother hand, a via hole is formed after formation of an interconnecttrench in an interlayer insulating film.

As illustrated in FIG. 27, a barrier insulating film 44 and aninterlayer insulating film 45 are deposited over a third-levelinterconnect 43. A stopper film 46 is formed in the interlayerinsulating film 45. An SiCN film of from about 10 nm to 100 nm thickdeposited by plasma CVD is used as the stopper film 46. Steps until thisstep are similar to those described referring to FIGS. 1 to 15 inEmbodiment 1.

As illustrated in FIG. 28, after formation of a photoresist film 51 overthe interlayer insulating film 45, the interlayer insulating film 45 isdry etched with the photoresist film 51 as a mask. By stopping etchingat the surface of the stopper film 46, interconnect trenches 52 and 53are formed in the interlayer insulating film 45 over the stopper film46. Here an antireflective film is not formed between the interlayerinsulating film 45 and the photoresist film 51, but the stopper film 46made of an SiCN film having a low optical reflectance has been formed inthe interlayer insulating film 45 as in Embodiment 1. Even if anantireflective film is not formed below the photoresist film 51,lowering of resolution, which will otherwise occur by an exposure lightreflecting from the surface of the third-level interconnect 43 andincident on the photoresist film 51, can be suppressed.

As illustrated in FIG. 29, after formation of a photoresist film overthe interlayer insulating film 45, the interlayer insulating film 45 andbarrier insulating film 44 are dry etched with the photoresist film 48as a mask, whereby a via hole 38 is formed and the third-levelinterconnect 43 is exposed from the bottom of the via hole 38. In thiscase, the stopper film 46 functions as an antireflective film so thatlowering of resolution, which will otherwise occur by an exposure lightreflecting from the surface of the third-level interconnect 43 andincident on the photoresist film 48, can be suppressed.

After removal of the photoresist film 48, a fourth-level interconnect 54is formed in the interconnect trench 52 and via hole 49, and a fuse 55is formed in the interconnect trench 53. The fourth-level interconnect54 and fuse 55 are formed in a similar manner to that described inEmbodiment 1.

It is possible to simplify the formation step of the fourth-levelinterconnect 54 also in this Embodiment in which the via hole 38 isformed after the formation of the interconnect trenches 52 and 53 in theinterlayer insulating film 45. In addition, the fourth-levelinterconnect 54 can be formed in a high yield.

The present invention made by the present inventors was describedspecifically based on some embodiments. The present invention is notlimited to these embodiments but it is needless to say that changes maybe made without departing from the scope of the present invention. Forexample, the present invention can be applied to a manufacturing methodof a semiconductor device having five or more Cu interconnect layers.

The present invention is effective when applied to a semiconductorintegrated circuit device having a multilevel interconnect formed by thedual damascene process.

The invention claimed is:
 1. A semiconductor integrated circuit device,comprising: (a) a first interconnect made of a first metal film andformed over a semiconductor substrate; (b) a first interlayer insulatingfilm formed over the first interconnect; (c) a first via hole forconnecting to the first interconnect formed in the first interlayerinsulating film; (d) a first interconnect trench for connecting to thefirst via hole formed in the first interlayer insulating film; (e) asecond interconnect and a first connection portion formed together byfilling a second metal film in the first interconnect trench and in thefirst via hole; (f) a third interconnect made of a third metal film andformed over the second interconnect and the first interlayer insulatingfilm; (g) a second interlayer insulating film formed over the thirdinterconnect; (h) a second via hole for connecting to the thirdinterconnect formed in the second interlayer insulating film; (i) asecond interconnect trench for connecting to the second via hole formedin the second interlayer insulating film; and (j) a fourth interconnectand a second connection portion formed together by filling a fourthmetal film in the second interconnect trench and in the second via hole;wherein a thickness of the second interlayer insulating film is largerthan a thickness of the first interlayer insulating film, wherein thesecond interlayer insulating film is divided by a stopper film providedtherein, wherein a bottom of the fourth interconnect is arrangedsubstantially at a level of the stopper film, wherein the firstinterlayer insulating film has no stopper film formed therein, wherein abottom of the second interconnect is arranged on the first interlayerinsulating film, wherein a depth of the second interconnect trench isgreater than a depth of the first interconnect trench, wherein the firstinterlayer insulating film is formed with an SiOC as a main component,wherein the second interlayer insulating film is formed with a siliconoxide or a fluorinated silicon oxide as a main component, wherein adiameter of the second via hole is greater than a diameter of the firstvia hole, wherein the first, second, third and fourth metal films areformed with copper as a main component, wherein a first barrierinsulating film which prevents diffusion of copper is formed on thefirst interconnect, formed under the first interlayer insulating filmand includes silicon, carbon and nitrogen, wherein a second barrierinsulating film is formed between the first barrier insulating film andthe first interlayer insulating film and does not include nitrogen,wherein a third barrier insulating film which prevents diffusion ofcopper is formed between the third interconnect and the secondinterlayer insulating film so as to be directly in contact with thethird interconnect and the second interlayer insulating film andincludes silicon, carbon and nitrogen, and wherein the etching stopperfilm includes silicon and nitrogen and is formed of a different materialfrom the first, second and third barrier insulating films.
 2. Asemiconductor integrated circuit device according to claim 1, furthercomprising a first barrier metal formed inside of the first interconnecttrench and the first via hole and formed between the first interlayerinsulating film and the second metal film.
 3. A semiconductor integratedcircuit device according to claim 1, further comprising a second barriermetal formed inside of the second interconnect trench and the second viahole and formed between the second interlayer insulating film and thefourth metal film.
 4. A semiconductor integrated circuit deviceaccording to claim 1, wherein the first interconnect trench is shallowerthan the first via hole, and the second interconnect trench is shallowerthan the second via hole.
 5. A semiconductor integrated circuit deviceaccording to claim 1, wherein the second via hole is deeper than thefirst via hole.
 6. A semiconductor integrated circuit device,comprising: (a) a first interconnect made of a first metal film andformed over a main surface of a semiconductor substrate; (b) a firstinterlayer insulating film formed over the first interconnect; (c) afirst via hole formed in the first interlayer insulating film andconnected to the first interconnect; (d) a first interconnect trenchformed in the first interlayer insulating film in a region including aregion in which the first via hole has been formed; (e) a secondinterconnect formed by filling a second metal film in the firstinterconnect trench and the first via hole; (f) a third interconnectmade of a third metal film and formed over the second interconnect andthe first interlayer insulating film; (g) a second interlayer insulatingfilm formed over the third interconnect; (h) a second via hole formed inthe second interlayer insulating film and connected to the thirdinterconnect; (i) a second interconnect trench formed in the secondinterlayer insulating film in a region including a region in which thesecond via hole has been formed; and (j) a fourth interconnect formed byfilling a fourth metal film in the second interconnect trench and thesecond via hole, wherein the second interlayer insulating film isthicker than the first interlayer insulating film, wherein an etchingstopper film is formed in the second interlayer insulating film, whereina bottom of the second interconnect trench is arranged near the etchingstopper film, wherein the first interlayer insulating film has noetching stopper film formed therein, wherein a depth of the secondinterconnect trench is greater than a depth of the first interconnecttrench, wherein the first interlayer insulating film is formed with anSiOC as a main component, wherein the second interlayer insulating filmis formed with a silicon oxide or a fluorinated silicon oxide as a maincomponent, wherein a diameter of the second via hole is greater than adiameter of the first via hole, wherein the first, second, third andfourth metal films are formed with copper as a main component, wherein afirst barrier insulating film which prevents diffusion of copper isformed on the first interconnect, formed under the first interlayerinsulating film and includes silicon, carbon and nitrogen, wherein asecond barrier insulating film is formed between the first barrierinsulating film and the first interlayer insulating film, wherein anitrogen concentration of the first barrier insulating film is largerthan a nitrogen concentration of the second barrier insulating film,wherein a third barrier insulating film which prevents diffusion ofcopper is formed between the third interconnect and the secondinterlayer insulating film so as to be directly in contact with thethird interconnect and the second interlayer insulating film andincludes silicon, carbon and nitrogen, and wherein the etching stopperfilm is formed of an SiN or an SiON, and is formed of a differentmaterial from the first, second and third barrier insulating films.
 7. Asemiconductor integrated circuit device according to claim 6, furthercomprising a first barrier metal formed inside of the first interconnecttrench and the first via hole and formed between the first interlayerinsulating film and the second metal film.
 8. A semiconductor integratedcircuit device according to claim 6, further comprising a second barriermetal formed inside of the second interconnect trench and the second viahole and formed between the second interlayer insulating film and thefourth metal film.
 9. A semiconductor integrated circuit deviceaccording to claim 6, wherein the first interconnect trench is shallowerthan the first via hole, and the second interconnect trench is shallowerthan the second via hole.
 10. A semiconductor integrated circuit deviceaccording to claim 6, wherein the second via hole is deeper than thefirst via hole.